1. Field of the Invention
The present invention relates to a connecting member that connects members to each other in a structure including a skeleton construction of, for example, a building or an automobile.
2. Description of the Related Art
A structure including a skeleton construction of, for example, a building or an automobile is formed by assembling a plurality of strength members, such as side frames. Connecting members that connect members to each other for disposing the members apart from each other with a certain gap being provided therebetween in such a structure, or for increasing the strength of such a structure are known (refer to, for example, a reinforcement strut tower 21 in FIG. 2 in Japanese Unexamined Patent Application Publication No. 2004-106704 (Patent Literature 1) and an inclined lower member 18 in FIGS. 2 and 3 in Japanese Unexamined Patent Application Publication No. 2009-184424 (Patent Literature 2)).
In general, such connecting members described above are formed by assembling a plurality of members (formed by pressing a metallic plate) and by fastening the assembled members to each other using welding, or a mechanical fastener such as a bolt. Here, when the members are welded together, the members may become distorted due to welding heat. Therefore, in order to fasten the members together with good precision without thermal distortion, a technology (such as that disclosed in Japanese Unexamined Patent Application Publication No. 2000-264246 (Patent Literature 3)) of clinching the members to each other by electromagnetic forming may be considered. That is, in Patent Literature 3, one of two pipe sections is fitted to an interior of the other of the pipe sections, and a flux concentrating unit of an electromagnetic forming device is placed in the vicinity of a portion where the two pipe sections overlap each other, to generate a magnetic field. This causes an electromagnetic force generated by an induction current to act upon the pipe sections, and the pipe sections to be compressed, as a result of which the members are clinched to each other.
However, when two pipe sections, formed of nonmagnetic materials such as aluminum, are clinched to each other by electromagnetic forming, induction current is similarly generated at the inner member as well as at the outer member. Therefore, the outer member and the inner member are both deformed in a diameter reduction direction. Consequently, sufficient clinching force is not obtained, as a result of sufficient strength may not be provided in the connecting member that connects the strength members of a structure to each other.
In recent years, there is an increasing demand for improving designability, and other members are often disposed between connection members that are to be connected by a connecting member. In such a case, it is necessary to form the connecting member with a shape that does not interfere with the members that are disposed between the connection members. As mentioned above, if the members that form a connecting member are formed by a pressing operation, it may be difficult to form the connecting member with a required shape.